A “handle” in Windows is a reference pointer to a resource like a file, registry key, process, or a section of memory. When an application (in this case, the SSQ activator) asks Windows to perform an action (like read/write to a file), it uses a handle. means the handle the activator provided to the system is no longer valid—it points to nothing, has already been closed, or was never created correctly.
The activator looks for an existing sw_d.lic file. If you previously attempted a manual crack and left behind a malformed license file (e.g., with spaces instead of tabs, or incorrect hostnames), the activator's arithmetic check on the file size or checksum will fail, throwing Error 6. Solidworks.2017.activator-ssq Error 6
Given that SolidWorks 2017 is now several years old, you may ask: Should I spend hours fixing Error 6? A “handle” in Windows is a reference pointer